A detective was responding to “an escalated series of threats” when he fatally shot an unarmed National Guardsman during a Grand Central Parkway traffic stop, his lawyer said yesterday.

Detective Hassan Hamdy, a 14-year veteran assigned to the elite Emergency Service Unit, told a Queens grand jury he opened fire on Noel Polanco last October when he thought the driver was reaching for a gun. No weapon was found.

Polanco was driving home a bartender from the lounge where he worked, along with her friend, an off-duty cop who was sleeping in the back seat.

“He was speeding, driving erratically, refusing to be pulled over by the police,” said Hamdy’s lawyer, Philip Karasyk. “Then, finally, Mr. Polanco refused to show his hands and lunged from the bottom of the car with both of his hands. There was no other conclusion that he could come to other than he was about to be met with deadly force.”